Autoradiography is a well-developed technique for imaging in the context of clinical medicine and research on biological processes. In this technique, a radioactive probe is administered to a patient or a subject or a tissue to provide an internal source of radiation, thus distinguishing this method from conventional radiography in which an external source of radiation is employed. Autoradiography is most commonly used for imaging of ex vivo samples obtained from tissue administered with a radioactive pharmaceutical. Thin slices (e.g., 5-50 μm thick) of the sample are subsequently analyzed using a high-resolution imaging detector sensitive to charged particles (e.g., alpha particles, beta particles and/or Auger electrons) emitted by the radioactive pharmaceutical. These techniques provide 2D images exhibiting high spatial resolution capable of resolving the distribution of a radioactive pharmaceutical at the cellular or subcellular level.
Although autoradiography provides a valuable approach for high-resolution imaging of tissue, this technique is significantly limited in its extension to 3D imaging of in vivo tissue. While reassembly of 2D slice image information to obtain a 3D image of a sample is feasible, this application of autoradiography is labor intensive and practically limited due to distortion of thin film slices introduced by dehydration and/or in transferring them to an imaging detector. Further, extension of conventional autoradiography to 3D imaging requires sectioning of the sample into thin slices to provide depth information, thereby effectively limiting the technique to application of ex vivo tissue samples.